1993 Toyota Corolla Corolla GLi 93 4afe engine

Good Day to you,

I am having problems when I am shifting from Neutral to 1st Gear coming from a stop, its like im starting on the 2nd gear, the engine is like going to stop and the RPM drops. But when the engine makes the pace it runs smooth. My guess it started when I changed my muffler to freeflow. Does is anyway affect the engine performance? Or, if I change my High Tension wires and sparkplugs to a performance brand like splitfire, will my engine run smooth? Thank you so much, you have been a great help to every one.